The life span of currently used traffic lights is limited by the life span of a driver or power supply of the traffic light powering the lights. For example, electrolytic capacitors are often used in drivers for lights as they offer large capacitance values in small sizes. However, they can limit the life of the driver due to drying of their electrolyte over several years.
Simply changing the electrolytic capacitor for another type of capacitor may not always be practical as other types of capacitors are much larger and/or more expensive for the same capacitance and voltage ratings. In addition, simply replacing electrolytic capacitors in an existing design with other types of lower capacitance can cause problems, such as for example, high output current ripple, stability and flicker.
Many traffic light systems rely on being able to detect a minimum current draw from a light to confirm operation of the light. Older filament bulbs and older light emitting diode (LED) technologies drew an easily measureable minimum current. But due to rapid advancement in lighting technologies, traffic lights have increased efficiency to the point where the current draw is sometimes below that is required by the traffic light controllers.